“Iron Man 3” pits genius billionaire Tony Stark, played with panache by Robert Downey Jr., against a terrorist plot that threatens to bring the most powerful people in the world to their knees. But that threat is not quite what it seems.

Reader beware: Spoilers lie ahead.

Guy Pearce in January 2013. (Jay L. Clendenin / Los Angeles Times)

Ben Kingsley’s Mandarin may be the face on the posters and the focus of the movie trailers, but lurking in the background is Aldrich Killian, another visionary genius like Stark, but one whose circumstances led him down darker paths. Killian, played by Emmy-winning actor Guy Pearce, is the founder of the private brain trust AIM, which helped develop the Extremis virus. Extremis imparts superhuman strength and regenerative powers to its subjects, and Killian takes full advantage of the effects.

In many ways, Killian is a foil for Stark, using his mind (and the scientific brilliance of his colleague Dr. Maya Hansen, played by Rebecca Hall) to lift himself from challenging beginnings, but finding the lure of power too difficult to resist.

Hero Complex sat down with Guy Pearce for a spoiler-filled conversation about his character.

HC: Marvel did such a great job keeping the scope of your role a secret.

GP: Well it’s a tricky one to talk about, isn’t it, because you don’t want to take anything away from what’s presented in the marketing of the film with Ben and his character, because he does the most incredible job of a horrifying terrorist. So his turn, when you finally see who he is, it’s hilarious, isn’t it? He’s just absolutely hilarious. That was great for me because I never saw any of it while they were filming it. I knew obviously that that’s what was going to happen, but I think it’s really important to not give that stuff away.

HC: And the first time we see you on screen at the beginning of the film, it’s nothing like what we’ve seen in the trailers. What was it like to undergo such a transformation?

GP: It was fun. We were concerned about going too far and actually not being able to recognize that that was the same guy from early on. We all wanted to portray him as somebody who was kind of difficult on all sorts of levels — that he had his own physical difficulties, he was difficult to be around ’cause he’s kind of irritating and annoying. And you know, we didn’t want him to be too sympathetic, because we also don’t want Tony to seem like a real [jerk] when he turns his back on him.

GP: He does, but what works, I think, is that Tony’s so kind of caught up in his own shtick at that point. So it’s a tricky balance to try and get right. It was funny because we shot that early stuff in the film right towards the end. So we’d sort of done all the lovely looking stuff, and then we went to Miami and did a bunch of stuff there, and I think that included the early part.

HC: He’s such a tragic character.

GP: Absolutely. And I think interestingly, I always feel some sympathy for anybody who does something bad out there, because you go, “There’s got to be a reason for it.” Not everybody who does something bad is a psychopath. And even somebody who is a psychopath, whether it’s genetic or whether it’s from experience, there’s something that has happened to them who has turned them this way. Even if you hate everything about them for everything that they’ve done, just the humanity in you needs to kind of find a place that goes, “That could have been me. I could have ended up being that person.” So I don’t know. Maybe I’m too sympathetic as an audience member, because audience members want their bad guys and they want their good guys, etc. But I do think the idea of digging yourself out of a hole and attaining power and kind of standing on your own two feet is one thing, but if that just keeps going, and your power just kind of gets out of control, I think there’s something to be said for self-control and being able to sort of get a handle on that. It’s funny, you know, there was a documentary thing on television about Nixon, about the Watergate thing. You kind of go, “God, did he… was he… something led to this.” And yet he ends up being one of the most hated people because of the one thing that he did — this went wrong, that went wrong, and he ended up over here. It’s hard not to feel sympathy for somebody.

HC: It makes Killian such a good foil for Tony Stark. Both geniuses, one came from privilege, one didn’t…

GP: Well absolutely. There’s so much to be said for all those emotional qualities that we have, negative ones as well. Envy and jealousy and denial and competition, and all this kind of stuff that we have swimming around in us all the time. We’re all so kind of fragile and precarious, and just one thing can shoot off in that direction and end up being that, and something can shoot up in that direction and you end up being king of the world. It’s just so amazing how much of a fine line there is between people.

HC: There’s the oft-quoted saying that villains are made and not born, but it’s not often in a blockbuster move we get to see how a villain is made, rather than being presented with a villain and asked to accept a backstory we don’t get to see. It’s great to get to see the before and after.

GP: I’d been working on both characters, both versions of the character at home before I came here, because to me, they were obviously clearly connected, even though the version of Killian that we see throughout the majority of the film is the Extremis-ized version you know. But at the same time, there has to be a truth to him. There has to be a feasible human being that can conceivably, he could have been born that way. So I had to feel like both of them were real completely and utterly real. But it is interesting that we do get to see where he’s come from, because as you say, you often don’t. And particularly, on a physical and physiological and emotional, such an extreme level, that you actually go from one type of person and change into another kind of person, and that just never happens to a character. I mean, you find an arc, generally, and often it’s about a character kind of realizing something about themselves more so than a physical transformation. So it was interesting to play such an extreme kind of change. I had to sort of understand how he goes from that to the villain that we see him being.

HC: That’s the harder jump.

GP: It is, and the thing that I think I got my head around was really, as I say, the propulsion. Like you propel yourself out of a dark hole to survive, but if that energy is kinetic, and it just keeps going, then it could turn into anything ultimately. It’s like anything, I suppose, when you’re dealing with science. If it goes this way, it’s positive, and if it goes that way, it’s negative. It was just about power and being swept up by that and losing control. It is sad, but it’s totally realistic, in a way.

HC: Do you think people will read unintended messages from the film in the wake of the Boston attacks?

GP: I have no idea, to be honest. I’m really generally terrible at trying to understand I think what people as a whole kind of take from things. I’m often surprised at the way people respond to things. I remember the first time years ago when I was young, and people saying, “Do you think it’s violent movies that make people be violent?” And I was like, “Wow, what a concept! Really? I never even considered such a thing.” Of course, ever since that was mentioned, I’m sort of looking for that everywhere. And there’s a part of you that goes, “Oh come on, no, of course not. I mean surely.” But then you go, “Well, maybe. Maybe.” But I do think it’s so raw. It’s unfortunate. You’ve got to look at “Gangster Squad”; they reshot a section of that because there was the shooting in a cinema. So you know, as we say, art and life kind of cross over, and sometimes it just kind of burns too hot at times.

HC: Is there a role in your career that prepared you for this one?

GP: I’m sure that on an evolutionary sort of level, everything kind of prepares you for the next thing in some sort of way. I look back at old roles, and I do it regularly. I looked at certain things and went, “Ooh, wow, I’m really rushing through that, aren’t I? I’d do that differently now.” So you feel yourself improving all the time on some level.